Sterilized package



Patented July 28, 1942 s'rnnmrzun memos I Cornelius M. Connor, Ardmore, Pa assignmto The Glassine Paper Company, West Conshohocken, Pa, a corporation of Delaware Application January '20, 1938, Serial No..185,840

2 Claims. (oi. zoo-cs2) This invention relates to a sterilized package, and particularly a glassine package containing gauze or similar material in sterilized form.

the accompanying drawing, in which the figure represents a sterile package produced in accordance with the invention.

Attempts have been heretofore made to pro-' vide sterilized ackages of gauze bandages or the like comprising glassine envelopes or wrappings, the advantage of the glassine being visibility and low permeation due to its greaseproof properties. Such attempts, however, have not been particularly satisfactorybecause the sterilizing temperatures used, at least 212 F., and more usually temperatures of 235 to 240 F., corresponding to a four pound steam pressure, maintained for a period of forty-five minutes to one hour, are such as to result in the disintegration of ordinary glassine to the extent that the glassine turns color, the result being a dirty brown which is, of course, highly objectionable in a supposedly sterile package. Furthermore, the paper becomes quite brittle and readily breaks in handling. The paper which thus disintegrates is ordinary glassine consisting, for example, of 100% bleached sulphite pulp with the addition of about of rosin size based on dry stock, 0.02 pbund of a blue phospho-tungstate lake per thousand pounds of dry stock and 1.25 to 1.5% of crystallized alum (based on dry stock), the latter amounting to 12 to 15 pounds per thousand pounds of the dry stock. Even though such paper has stood the formation conditions involving heating over the driers and. then supercalendering, it will disintegrate and turn brown in the sterilizer. The

. conditions of formation involve the exposure to high temperatures only for a very short period, and furthermore, during the drying process there is such dilution with water that disintegration,

probably due to the causes presently described,

will not take place.

My experiments have indicated that the disintegration and discoloration is probably due to the formation of sulphuric acid in fairly concentrated form by hydrolysis of the free alum in the paper. Both in the presence of steam and in the presence of dry heat, hydrolysis may occur because the glassine contains a considerable amount of inherent moisture. At sterilization temperatures of the amounts indicated above, the sulphuric acid is probably liberated and is in such a concentrated condition as to cause dehydration of the cellulose resulting in disintegration and discoloration above mentioned.

In accordance with the present invention, these undesirable results are obviated by the utilization of special glassine for the formation of the pack- In the drawing. the package is shown as comprising a bandage indicated at 2 within an improved glassine envelope indicated at 4.

Instead of utilizing for the formation of the container glassine of the type heretofore used, I

ingthe rosin size is of such amount that the concentration of the sulphuric acid apparently produced by hydrolysis does not afiect the paper. The test for a satisfactory paper of the type just described is for its total acidity determined by extracting the paper with water, refluxing to avoid loss, and titrating with a weak sodium hydroxide solution. The acidity thus determined may, for specification purposes, be assumed to be wholly due to sulphuric acid, which, in fact, is substantially the case. Experiments indicate that an amount of sulphuric acid not more than 0.1%

of the air dry weight of the glassine tested and preferably not more than 0.075% of the air dry weight Of the glassine being tested will indicate a satisfactory paper adapted to be sterilized without disintegration or discoloration. Heretofore, the glassine papers used have generally contained 0.15% to 0.3% or more sulphuric acid shown by the extraction test just described. it appears that a sulphuric acid content of over 0.1% will give rise to an unsatisfactory product from the standpoint OI both disintegration and discoloration.

.l'he glassinepaper is formed in conventional fashion by sheeting, moistening and supercalendermg in the usual way, subJect to the limitation on the addition or alum to give rise to the acidity conditions indicated by the above mentioned test.

'lhe blue dye used,' preferably the blue tetra azo direct dye, is substantially more heat resistant than the lake heretofore used, possibly because 01 the fact that it actuahy eyes the noers rather than merely coats them. The blue dye is desirable because it will make a slightly yellow gauze appear white when viewed through the envelope.

age,'the nature of which will be apparent from The Particular dye used 1 Sum as 1105 be affected by small changes in hydrogen ionc'oncentration, and consequently the color is not affected by the liberation of sulphuric acid during the sterilization process.

Preferably, the container, after formation from the glassine of the preferable type described above and after the insertion of the contents which are to be sterilized, and suitable sealing, is subjected to the conventional sterilization process involving exposure to a temperature of about 235 to 240? F. for a period of 45 minutes.

While the above procedure is desirable, it is possible to achieve the same results consistent with the addition of a larger amount of alum. For example, if alum is added in the amounts previously used, say to the amount of 1.25% to 1.5% of crystallized alum based on dry stock; the possibility of the formation of sulphuric acid by hydrolysis may be avoided by the addition, for

example, after the addition of the rosin size and alum, of borax in the calculated amount required to provide a liberation of boric acid instead of sulphuric acid in the final product under conditions of hydrolysis. alkalinity, the borax may be admixed with boric acid. Under such conditions, the test for total acidity isthe same, that is, upon extraction as indicated above, the free sulphuric acid obtainable (differentiated from the boric acid by the use of a suitable indicator in the titration in well known fashion) should be lessthan 0.1% and preferably nomore than 0.075% of the air-dry -glassine weight.

Another alternative procedure involves the neutralization of the free acidity bythe treatment of the paper on the paper machine with suitable amounts of dilute solutions of lime,

sodium carbonate, sodium aluminate or the like to secure in the final product the same type of results as those indicated above, that is, an extractible sulphuric acid content of not more than 0.1%, and preferably less than 0.075% of the airdry glassine weight. Where sulphuric acid is In order to avoid excess and said glassine being and discoloration the only acid which may be extracted by'the.

treatment indicated above, it is only necessary that the total acidity should be determined, since the major portion of this will undoubtedly be due to sulphuric acid, On the other hand, where another acid may beextracted as, for example, boric acid, distinction may be made in the titration-.to secure an indication of the sulphuric acid content, since the presence of large amounts of total acidity will not be harmful if the sulphuric acid content is below the limit specified.

What I claim and desire to protect by Letters 'Patent is: v

1. A sterile package comprising a container and contents subjected to a sterilizing temperature, the container comprising glassine made of sulphite pulp containing small amounts of rosin size and alum, the extractible sulphuric acid content being not more than 0.10% of the air-dry glassine weight, and said glassine being resistant to disintegration and discoloration at sterilizinz temperatures.

2.' A container for material requiring sterilization at an elevated temperature, said container comprising glassine made of sulphite pulp containing small amounts of rosin size and alum, the extractible sulphuric acid content being not more than 0.10% of the air-dry glassine weight, resistant to disintegration at sterilizing temperatures.

CORNELIUS M. CONNOR. 

